OPERATIONS WITH DECIMALS 2.1.1 ARITHMETIC OPERATIONS WITH DECIMALS ADDING AND SUBTRACTING DECIMALS: Write the problem in column form with the decimal points in a vertical column. Write in zeros so that all decimal parts of the number have the same number of digits. Add or subtract as with whole numbers. Place the decimal point in the answer aligned with those above. MULTIPLYING DECIMALS: Multiply as with whole numbers. In the product, the number of decimal places is equal to the total number of decimal places in the factors (numbers you multiplied). Sometimes zeros need to be added to place the decimal point. DIVIDING DECIMALS: When dividing a decimal by a whole number, place the decimal point in the answer space directly above the decimal point in the number being divided. Divide as with whole numbers. Sometimes it is necessary to add zeros to the number being divided to complete the division. When dividing decimals or whole numbers by a decimal, the divisor must be multiplied by a power of ten to make it a whole number. The dividend must be multiplied by the same power of ten. Then divide following the same rules for division by a whole number. For additional information, see the Math Notes boxes in Lessons..2 and.. of the Core Connections, Course 2 text. Example 1 Add 47.7, 28.9, 14.56, and 7.8. 47.7 28.90 14.56 + 7.80 98.6 Example 4 Multiply 0.7 by 0.0004. 0.7 (2 decimal places ) x 0.0004 (4 decimal places) 0.000148 (6 decimal places) Example 2 Subtract 198.76 from 47.2. 47.20 198.76 274.44 Example 5 Divide 2.4 by 8. 4.05 8) 2.40 2 0 40 40 0 Example Multiply 27.2 by 14.5. 27. 2 (2 decimal places ) x 14. 5 ( 2 decimal places ) 8196 1660 10928 272 96.9596 (4 decimal places) Example 6 Divide 27.42 by 1.2. First multiply each number by 10 1 or 10. 22.85 1.2 27.42 12 274.2 12 274.20 24 4 24 10 2 96 60 60 0 Parent Guide with Extra Practice 201 CPM Educational Program. All rights reserved. 15
Problems 1. 4.7 + 7.9 2..9 + 2.82. 8.72 + 6.7 4. 58. + 72.84 5. 4.7 + 692 6. 428 + 7.92 7. 42.108 + 14.7 8. 9.87 + 87.4796 9. 9.999 + 0.001 10. 0.0001 + 99.9999 11. 0.017 + 1.78 12. 2.07 + 0.0987 1. 15. + 72.894 14. 47.9 + 68.07 15. 289.07 + 15.98 16. 476.84 + 27.847 17. 15.8 + 27.4 + 9.076 18. 48.2 + 284. + 4.68 19. 278.6 + 47.042 + 21.6 20. 47.68 + 28.00476 + 84. 21. 8.7 4.6 22. 9.8 7.5 2. 8.12 6.98 24. 7.045.76 25. 6.04.68 26. 8.021 4.7 27. 14 7.41 28. 2 15.7 29. 10 4.652 0. 18 9.04 1. 0.82 0.47 2. 0.647 0.9. 1.4 0.058 4. 2.07 0.52 5. 4.2 1.764 6..8 2.406 7. 8.42 2.605 8. 47.1 42.70 9. 15.68 + 14.4 18.576 40. 87.4 15.687 28.06 41. 7.4 6.4 42..71 4.0 4. 0.08 4.7 44. 0.04.75 45. 41.6 0.02 46. 9.4 0.005 47..07 5.4 48. 4.02.02 49. 0.004 0.005 50. 0.007 0.0004 51. 0.25 0.4 52. 4.2 0.0072 5. 0.0006 0.0001 54. 0.0005 0.00026 55. 8.8 0.0001 56. 47.6 0.000001 57. 0.078.1 58. 0.04 4.2 59. 50 0.004 60. 421 0.00005 16 201 CPM Educational Program. All rights reserved. Core Connections, Course 2
Divide. Round answers to the hundredth, if necessary. 61. 14. 8 62. 18.2 5 6. 147. 6 64. 46.6 12 65. 100.2 24 66. 12.7 28 67. 47. 0.002 68. 5.6 0.004 69. 500 0.004 70. 420 0.05 71. 1.2 0.02 72..486 0.012 7. 46. 0.011 74. 5.7 0.02 75. 25.46 5.05 76. 26.5 2.2 77. 6.042 0.006 78. 7.05 0.005 79. 207. 4.4 80. 06.4.2 Answers 1. 12.6 2. 6.75. 45.42 4. 11.14 5. 696.7 6. 45.92 7. 56.88 8. 97.496 9. 10.000 10. 100.0000 11. 1.797 12. 2.1087 1. 88.194 14. 115.97 15. 05.245 16. 504.21 17. 51.856 18. 7.258 19. 47.272 20. 459.98476 21. 4.1 22. 1.88 2. 1.2 24..285 25. 2.624 26..651 27. 6.569 28. 7.6 29. 5.48 0. 8.957 1. 0.62 2. 0.257. 1.2862 4. 1.547 5. 2.46 6. 1.94 7. 5.815 8. 4.427 9. 11.204 40. 4.7067 41. 46.976 42. 14.951 4. 0.76 44. 0.15 45. 12.562 46. 0.04982 47. 16.578 48. 12.14946 49. 0.000020 50. 0.0000028 51. 0.10105 52. 0.01104 5. 0.000000078 54. 0.00000010 55. 0.00088 56. 0.000476 57. 0.2418 58. 0.1806 59. 1.4 60. 0.02105 61. 1.7875 or 1.79 62..664 or.66 6. 24.55 64..86 or.86 65. 4.18 66. 4.74 67. 2,650 68. 1,400 69. 125,000 70. 8400 71. 41.25 72. 29.05 7. 4209.09 74. 24.78 75. 5.04 76. 11.98 77. 1007 78. 1407 79. 47.11 80. 95.75 Parent Guide with Extra Practice 201 CPM Educational Program. All rights reserved. 17
FRACTION-DECIMAL-PERCENT EQUIVALENTS 2.1.1 and 2.1.2 Fractions, decimals, and percents are different ways to represent the same portion or number. fraction words or pictures decimal percent Representations of a Portion For additional information, see the Math Notes box in Lesson 2.1.2 of the Core Connections, Course 2 text. For additional examples and practice, see the Core Connections, Course 2 Checkpoint 2 materials. Examples Decimal to percent: Multiply the decimal by 100. (0.81)(100) = 81% Fraction to percent: Write a proportion to find an equivalent fraction using 100 as the denominator. The numerator is the percent. 4 5 = x 100 so 4 5 = 80 100 = 80% Decimal to fraction: Use the digits in the decimal as the numerator. Use the decimal place value name as the denominator. Simplify as needed. Percent to decimal: Divide the percent by 100. 4% 100 = 0.4 Percent to fraction: Use 100 as the denominator. Use the percent as the numerator. Simplify as needed. 22% = 22 100 = 11 50 56% = 56 100 = 14 25 Fraction to decimal: Divide the numerator by the denominator. 8 = 8 = 0.75 5 8 = 5 8 = 0.625 a. 0.2 = 2 10 = 1 5 b. 0.17 = 17 100 11 = 11 = 0.2727 = 0.27 To see the process for converting repeating decimals to fractions, see problem 2-22 in the Core Connections, Course 2 text or the Math Notes box referenced above. 18 201 CPM Educational Program. All rights reserved. Core Connections, Course 2
Problems Convert the fraction, decimal, or percent as indicated. 1. Change 1 4 to a decimal. 2. Change 50% into a fraction in lowest terms.. Change 0.75 to a fraction in lowest terms. 4. Change 75% to a decimal. 5. Change 0.8 to a percent. 6. Change 1 5 7. Change 0. to a fraction. 8. Change 1 8 to a percent. to a decimal. 9. Change 1 to a decimal. 10. Change 0.08 to a percent. 11. Change 87% to a decimal. 12. Change 5 to a percent. 1. Change 0.4 to a fraction in lowest terms. 14. Change 65% to a fraction in lowest terms. 15. Change 1 9 to a decimal. 16. Change 125% to a fraction in lowest terms. 17. Change 8 5 to a decimal. 18. Change.25 to a percent. 19. Change 1 to a decimal. 16 Change the decimal to a percent. 20. Change 1 7 to a decimal. 21. Change 4% to a fraction. Change the fraction to a decimal. 2. Change 7 to a decimal. 8 Change the decimal to a percent. 22. Change 0.75 to a percent. Change the percent to a fraction. 24. Change 0.12 to a fraction 25. Change 0.175 to a fraction Parent Guide with Extra Practice 201 CPM Educational Program. All rights reserved. 19
Answers 1. 0.25 2. 1 2. 4 4. 0.75 5. 8% 6. 20% 7. 10 8. 0.125 9. 0. 10. 8% 11. 0.87 12. 60% 1. 2 5 14. 1 20 15. 0.11 16. 5 4 or 1 1 4 17. 1.6 18. 25% 19. 0.0625; 6.25% 20. 0.142859 21. 4 100 ; 0.4 22. 7 1 2 %; 8 2. 0.875; 87.5% 24. 12 99 = 4 25. 175 999 20 201 CPM Educational Program. All rights reserved. Core Connections, Course 2
OPERATIONS WITH INTEGERS 2.2.1 to 2.2. ADDITION OF INTEGERS Students review addition of integers using two concrete models: movement along a number line and positive and negative integer tiles. To add two integers using a number line, start at the first number and then move the appropriate number of spaces to the right or left depending on whether the second number is positive or negative, respectively. Your final location is the sum of the two integers. To add two integers using integer tiles, a positive number is represented by the appropriate number of (+) tiles and a negative number is represented by the appropriate number of ( ) tiles. To add two integers start with a tile representation of the first integer in a diagram and then place into the diagram a tile representative of the second integer. Any equal number of (+) tiles and ( ) tiles makes zero and can be removed from the diagram. The tiles that remain represent the sum. For additional information, see the Math Notes box in Lesson 2.2.4 of the Core Connections, Course 2 text. Example 1 4 + 6 Example 2 2 + ( 4) 6 5 4 2 1 0 1 2 4 5 6 5 4 2 1 0 1 2 4 5 4 + 6 = 2 Example Example 4 2 + ( 4) = 6 5 + ( 6) Start with tiles representing the first number. + + + + + Add to the diagram tiles representing the second number. + + + + + + 7 + + + + 7 = 4 + + + + Circle the zero pairs. 1 is the answer. + + + + + 5 + ( 6) = 1 Parent Guide with Extra Practice 201 CPM Educational Program. All rights reserved. 21
ADDITION OF INTEGERS IN GENERAL When you add integers using the tile model, zero pairs are only formed if the two numbers have different signs. After you circle the zero pairs, you count the uncircled tiles to find the sum. If the signs are the same, no zero pairs are formed, and you find the sum of the tiles. Integers can be added without building models by using the rules below. If the signs are the same, add the numbers and keep the same sign. If the signs are different, ignore the signs (that is, use the absolute value of each number.) Subtract the number closest to zero from the number farthest from zero. The sign of the answer is the same as the number that is farthest from zero, that is, the number with the greater absolute value. Example For 4 + 2, 4 is farther from zero on the number line than 2, so subtract: 4 2 = 2. The answer is 2, since the 4, that is, the number farthest from zero, is negative in the original problem. Problems Use either model or the rules above to find these sums. 1. 4 + ( 2) 2. 6 + ( 1). 7 + ( 7) 4. 10 + 6 5. 8 + 2 6. 12 + 7 7. 5 + ( 8) 8. 10 + ( 2) 9. 11+ ( 16) 10. 8 + 10 11. 7 + 15 12. 26 + 12 1. + 4 + 6 14. 56 + 17 15. 7 + ( 10) + ( ) 16. 95 + 26 17. 5 + ( 6) + 8 18. 11 + 274 19. 105 + ( 65) + 20 20. 6 + 2 + ( 4) + + 5 21. 5 + ( ) + ( 2) + ( 8) 22. 6 + ( ) + ( 2) + 9 2. 6 + ( ) + 9 24. 20 + ( 70) 25. 12 + ( 7) + ( 8) + 4 + ( ) 26. 26 + ( 1) 27. 16 + ( 8) + 9 28. 12 + ( 1) + 18 + ( 16) 29. 50 + ( 70) + 0 0. 19 + ( 1) + ( 5) + 20 22 201 CPM Educational Program. All rights reserved. Core Connections, Course 2
Answers 1. 2 2. 5. 0 4. 4 5. 6 6. 5 7. 1 8. 12 9. 27 10. 2 11. 8 12. 14 1. 7 14. 7 15. 6 16. 69 17. 7 18. 161 19. 60 20. 0 21. 8 22. 2 2. 0 24. 50 25. 2 26. 9 27. 15 28. 1 29. 10 0. 21 Parent Guide with Extra Practice 201 CPM Educational Program. All rights reserved. 2
OPERATIONS WITH INTEGERS 2.2.4 MULTIPLICATION AND DIVISION OF INTEGERS Multiply and divide integers two at a time. If the signs are the same, their product will be positive. If the signs are different, their product will be negative. Follow the same rules for fractions and decimals. Remember to apply the correct order of operations when you are working with more than one operation. For additional information, see the Math Notes box in Lesson.2.4 of the Core Connections, Course 2 text. Examples a. 2 = 6 or 2 = 6 b. 2 ( ) = 6 or (+2) (+) = 6 c. 2 = 2 or 2 = 2 d. ( 2) ( ) = 2 or ( ) ( 2) = 2 e. ( 2) = 6 or ( 2) = 6 f. ( 2) = 2 or ( 2) = 2 g. 9 ( 7) = 6 or 7 9 = 6 h. 6 9 = 7 or 9 ( 6) = 1 7 24 201 CPM Educational Program. All rights reserved. Core Connections, Course 2
Problems Use the rules above to find each product or quotient. 1. ( 4)(2) 2. ( )(4). ( 12)(5) 4. ( 21)(8) 5. (4)( 9) 6. (1)( 8) 7. (45)( ) 8. (105)( 7) 9. ( 7)( 6) 10. ( 7)( 9) 11. ( 22)( 8) 12. ( 127)( 4) 1. ( 8)( 4)(2) 14. ( )( )( ) 15. ( 5)( 2)(8)(4) 16. ( 5)( 4)( 6)( ) 17. ( 2)( 5)(4)(8) 18. ( 2)( 5)( 4)( 8) 19. ( 2)( 5)(4)( 8) 20. 2( 5)(4)( 8) 21. 10 ( 5) 22. 18 ( ) 2. 96 ( ) 24. 282 ( 6) 25. 18 6 26. 48 4 27. 121 11 28. 85 85 29. 76 ( 4) 0. 175 ( 25) 1. 108 ( 12) 2. 161 2. 22 ( 22) 4. 54 ( 6) 5. 1992 ( 24) 6. 1819 ( 17) 7. 1624 29 8. 1007 ( 5) 9. 994 ( 14) 40. 2241 27 Answers 1. 8 2. 12. 60 4. 168 5. 6 6. 104 7. 15 8. 75 9. 42 10. 6 11. 176 12. 508 1. 64 14. 27 15. 20 16. 60 17. 20 18. 20 19. 20 20. 20 21. 2 22. 6 2. 2 24. 47 25. 26. 12 27. 11 28. 1 29. 19 0. 7 1. 9 2. 7. 1 4. 59 5. 8 6. 107 7. 56 8. 19 9. 71 40. 8 Parent Guide with Extra Practice 201 CPM Educational Program. All rights reserved. 25
OPERATIONS WITH FRACTIONS 2.2.5 and 2.2.6 MULTIPLICATION OF FRACTIONS Multiplication of fractions is reviewed using a rectangular area model. Lines that divide the rectangle to represent one fraction are drawn vertically, and the correct number of parts are shaded. Then lines that divide the rectangle to represent the second fraction are drawn horizontally and part of the shaded region is darkened to represent the product of the two fractions. Example 1 1 2 5 8 (that is, 1 2 of 5 8 ) Step 1: Draw a generic rectangle and divide it into 8 pieces vertically. Lightly shade 5 of those pieces. Label it 5 8. Step 2: Use a horizontal line and divide the generic rectangle in half. Darkly shade 1 2 of 5 and label it. 8 Step : Write a number sentence. 1 2 5 8 = 5 16 The rule for multiplying fractions derived from the models above is to multiply the numerators, then multiply the denominators. Simplify the product when possible. For additional information, see the Math Notes box in Lesson 2.2.5 of the Core Connections, Course 2 text. 26 201 CPM Educational Program. All rights reserved. Core Connections, Course 2
Example 2 a. 2 2 7 2 2 7 4 21 b. 4 6 7 6 4 7 18 28 9 14 Problems Draw an area model for each of the following multiplication problems and write the answer. 1. 1 1 6 2. 1 4 5. 2 5 9 Use the rule for multiplying fractions to find the answer for the following problems. Simplify when possible. 4. 1 2 5 5. 2 2 7 6. 4 1 5 7. 2 5 2 8. 2 1 4 9. 5 6 2 10. 4 5 4 11. 2 15 1 2 12. 7 1 2 1. 8 4 5 14. 2 9 5 15. 10 5 7 16. 5 11 6 7 17. 5 6 10 18. 10 11 5 19. 5 12 5 20. 7 9 5 14 Answers 1. 1 18 2. 20. 10 27 4. 2 15 5. 4 21 6. 20 7. 4 15 8. 2 12 = 1 6 9. 10 18 = 5 9 10. 12 20 = 5 11. 2 0 = 1 15 12. 14 1. 12 40 = 10 14. 6 45 = 2 15 15. 15 70 = 14 16. 0 77 17. 15 60 = 1 4 18. 0 55 = 6 11 19. 15 60 = 1 4 20. 5 126 = 5 18 Parent Guide with Extra Practice 201 CPM Educational Program. All rights reserved. 27
ORDER OF OPERATIONS.1.1 and.1.2 When students are first given expressions like + 4 2, some students think the answer is 14 and some think the answer is 11. This is why mathematicians decided on a method to simplify an expression that uses more than one operation so that everyone can agree on the answer. There is a set of rules to follow that provides a consistent way for everyone to evaluate expressions. These rules, called the Order of Operations, must be followed in order to arrive at a correct answer. As indicated by the name, these rules state the order in which the mathematical operations are to be completed. For additional information, see the Math Notes box in Lesson.1.2 of the Core Connections, Course 2 text. For additional examples and practice, see the Core Connections, Course 2 Checkpoint 5 materials. The first step is to organize the numerical expression into parts called terms, which are single numbers or products of numbers. A numerical expression is made up of a sum or difference of terms. Examples of numerical terms are: 4, (6), 6(9 4), 2 2, (5 + 2 ), and 16 4 6. For the problem above, + 4 2, the terms are circled at right. + 4 2 Each term is simplified separately, giving + 8. Then the terms are added: + 8 = 11. Thus, + 4 2 = 11. Example 1 2 2 + (6 ) + 10 To evaluate an expression: Circle each term in the expression. Simplify each term until it is one number by: Simplifying the expressions within the parentheses. Evaluating each exponential part (e.g., 2 ). Multiplying and dividing from left to right. Finally, combine terms by adding or subtracting from left to right. 2 2 + (6 ) + 10 2 2 + () + 10 2 9 + () + 10 18 + 9 + 10 27 + 10 7 28 201 CPM Educational Program. All rights reserved. Core Connections, Course 2
Example 2 5 8 2 2 + 6 ( 5 + 4 ) 5 2 a. Circle the terms. b. Simplify inside the parentheses. c. Simplify the exponents. d. Multiply and divide from left to right. Finally, add and subtract from left to right. a. 5 8 2 2 + 6 ( 5 + 4 ) 5 2 b. 5 8 2 2 + 6 ( 9) 5 2 c. 5 8 4 + 6 ( 9) 25 d. 5 2 + 54 25 2 Example 20 + 5+7 42 + 12 4 a. Circle the terms. b. Multiply and divide left to right, including exponents. Add or subtract from left to right. a. 20 + 5+7 42 + 12 4 b. 20 + 4 16 + 11 Parent Guide with Extra Practice 201 CPM Educational Program. All rights reserved. 29
Problems Circle the terms, then simplify each expression. 1. 5 + 4 2. 10 5 +. 2(9 4) 7 4. 6(7 + ) + 8 2 5. 15 + 7(8 + 1) 6 6. 9 + 5 2 2(14 5) 7. 20 6+4 + 7 2 2 8. 5+0 7 + 6 2 18 9 9. 2 + 8 16 8 2 10. 25 5 2 + 9 2 11. 5(17 7) + 4 8 12. (5 2) 2 + (9 + 1) 2 1. 4 2 + 9(2) 6 + (6 1) 2 14. + 5 2 5 15. (7 2)2 + 8 4 6 5 16. 14 2 + 6 8 2 (9 ) 2 17. 27 + 18 9 ( + 4)2 18. 26 2 4 (6 + 4) 2 + (5 2) 19. 42+ ( 5 ) 2 + 2 ( 5 2) 2 18 Answers 1. 19 2. 5. 70 4. 64 5. 62 6. 0 7. 9 8. 9 9. 12 10. 0 11. 54 12. 109 1. 44 14. 5 15. 47 16. 5 17. 25 18. 6 19. 10 0 201 CPM Educational Program. All rights reserved. Core Connections, Course 2